The ‘Posa’ system practiced by some tribes involved:

The correct answer is: a) Collection of tributes from neighboring villages.

The Poșa system is a traditional system of taxation practiced by some tribes in the Indian subcontinent. Under this system, the headman of a village would collect a tribute from each household in the village, which would then be paid to the local ruler. The tribute was usually paid in kind, in the form of grain, livestock, or other goods.

The Poșa system was a way for the local ruler to extract resources from the villages under his control. It was also a way for the headman to maintain his authority over the village. The Poșa system was abolished in most parts of India in the 19th century, but it continues to be practiced in some remote areas.

Option b) is incorrect because religious ceremonies are not a form of taxation. Option c) is incorrect because barter trade is not a form of taxation. Option d) is incorrect because shifting cultivation is a form of agriculture, not a form of taxation.